Advice on modifications to TDA8932 amplifier.
I have built a simple amplifier using the TDA8932 circuit, two bose "twiddlers" (273488004), and a mono guitar jack socket. 24v 2.2A power supply.
I found this page with various modifications done to the board:
But the information isn't very extensive, no diagrams and circuits, no instructions.
What modifications could i do? he recomends externaly adding power-line decoupling capacitors, i have the exact type he recomends, but doesn't say where to wire them exactly.
He also appears to have caps connected to the input terminals, not sure what that does.
I'm looking for more info on these modifications, names of the techniques/mods, so i could read up more.
exact step by step instructions would be ideal, obviously, if you have the time, but who does these days.
any info, or info sources, are greatly appreciated, thanks.
the admin should move this thread to the class D forum.
her is the link from guys (later in the thread..) which know the tda8932 very well
Fasten seat belts. TDA8932 pessimistic review.
Chris is right, this topic should be under "Class D". It is not obvious as the TDA8932 is an amplifier in a single chip (chip-amp) but because we have a particular class D section, we use "Chip Amps" for class A and AB and a few more rare topologies.
On the site you refer to, I see 5 suggestions for improvement of that board. I have listed them in order of importance:
1) The power supply line decoupling capacitors are insufficient for bass reproduction. There is in total 5x100uF decoupling on the board. The supply current can be several amperes. The suggestion is to add 4700uF-15000uF capacitance external of the board. This suggestion must be for a stereo version with two boards.
The photos show no such extra capacitors. For one board and feed from an SMPS, 4700uF (50V) should be sufficient. There is no extra place for further capacitance on the small amplifier board. The external capacitor should be placed near the supply terminals of the board, eventually on the supply terminals and pointed away from the other components
2) The output filter chokes are insufficient in current rating to handle the output current. They are simply too small. If they saturate, it can have serious consequences for the output. Filter chokes that can handle the output current safely are necessarily larger in physical size. From the photos you see two different replacements with toroidal chokes. Another option is to move the output filter (chokes and capacitors) to an external board, placed close to the amplifier board and connected with short wires.
3) The output filter capacitors are of the ceramic SMD type with poor linearity. There is no space on the small board for replacement by foil capacitors with better linearity. If you anyway move the filter chokes to a board external of the amplifier board, use foil capacitors instead. If the chokes stay on the small amplifier board, leave the SMD capacitors as they are.
4) The chip cooling is poor and the chip will be hot above 20V supply. Luckily it is possible to mount a heatsink on top of the IC and this way leave operation up to 36V supply possible. The first photo shows two small green heatsinks mounted on top. You may add a small fan to ventilate the heatsinks. Another possibility is to use a heat-bridge from the IC and to the board edge and there connect a larger heatsink.
5) The input coupling capacitors are of a small ceramic SMD type with poor linearity and noisy. As you use the amplifier for a guitar, a slight increase in THD is not problematic. The noise level is anyway low. From the photos it seems not to be easy to replace the small SMD capacitors with foil capacitors (the blue ones), and I suggest you leave the SMD capacitors as they are.
As Think says, do not “repair” something that you actually find works quite well. And, remember the statement of Turbowatch2 that start modifying a cheap board designed for simple use, if you really want something better, is not worth the effort. Then buy something that is better implemented,
In my view, the TDA8932 chip has an enormous potential if implemented right but this very cheap board only allows simple performance.
Typical example of a cheap mass produced pcb made down to a price.
If you can change it tidily then it should be much better.
My preferred route has always been to design my own then I can make it right to start with. Use the best circuit options from the app notes if there are any or use datasheet.
However, great care needs to be taken with pcb layout if you dont want noise or oscillation. I would also add extra decoupling on the amplifier pcb.
Hi to all
as you wrote...for a try and playing around this boards are ok...but if you dont have the possibility to design a pcb and you want to get the real TDA8932 then i would prefer matt garman´s (and ohter´s) pcb !
its great and very well designed...
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